Common Name: Sweet Corn

General Information

Zea mays is an erect, robust, usually unbranched annual plant; it can grow up to 6 metres tall but is more likely to around 2 metres with cultivars that can range from around 1 metre up to 3 metres or more.
Maize is one of the most commonly cultivated crops in the world, providing a range of foods including popcorn, sweetcorn and a grain that can be ground into a flour. It was first domesticated in the Americas around 4,000 BC, but its cultivation has since spread to most parts of the world.[, ]. The plant also has a wide range of other uses. It is often used in herbal medicine, being valued especially as a diuretc, and has a range of other uses including as a material for thatching, fibre for paper and cellulose production, oil, adhesive etc.

Known Hazards

None known

Botanical References

Range

Original habitat is obscure, probably S. America or Mexico

Habitat

Not known in the wild.

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	2.00 m
Growth Rate	Fast
Pollinators	Wind
Cultivation Status	Cultivated

Cultivation Details

Zea mays requires a warm to hot growing season in order to produce a good crop. Different varieties have differing requirements as to how long that season is. Sweetcorn, for example, is harvested when the cobs when the seeds are still maturing and so needs a shorter growing season than a variety grown for its mature, dried seed. The period from planting to harvesting varies considerably. It may be as short as 70 days in some extra early cultivars, whilst it can be as long as 200 days in some very late cultivars[]. Plants can be grown from the temperate zone to lowland tropical areas and can succeed at elevations up to 2,000 metres in the tropics[]. They grow better in climates where the average rainfall is in the region of 800 - 1,200mm per annum[]. A temperature of 20 - 24°c is best for optimum growth[]. Heavy rainfall and temperatures in excess of 35°c adversely affect pollination and the quality of the seed[].
Grows best in a sunny position[]. Succeeds in a wide variety of soils, but well-drained, humus-rich, medium loams are generally preferable[]. Requires a rich soil if it is to do well[]. Requires a warm position a well drained soil and ample moisture in the growing season[, ]. Prefers a pH in the range 5.5 to 6.8[]. Crops grown on more acid soils are likely to produce lower yields[].
This species photosynthesizes by a more efficient method than most plants. Called the 'C4 carbon-fixation pathway', this process is particularly efficient at high temperatures, in bright sunlight and under dry conditions[].
Climatic conditions, latitude and altitude influence growth duration. In tropical highland areas it may take 9 - 10 months to reach maturity[].
Maize is predominantly cross-pollinating (90 - 95%), but is also self-fertile[].
Maize has the highest yield potential among the cereal crops. The average world yield of maize is 4.4 tonnes per hectare, but grain yields over20 tonnes are possible. Average grain yields of maize in tropical Africa are about 1.25 tonnes, varying greatly from less than 1 tonne for smallholders to about 6 tonnes in commercial farms[].
There are five main forms of corn, these have been classified as follows:-
Sweetcorn is of fairly recent development. It has very sweet, soft-skinned grains that can be eaten raw or cooked before they are fully ripe. Fast-maturing cultivars have been developed that can produce a worthwhile crop even in more northerly latitudes if a suitable warm sunny sheltered site is chosen[, ].
Popping corn is a primitive form with hard-skinned grains. When roasted, these grains 'explode' to form the popular snack 'popcorn'[].
Waxy corn is used mainly in the Far East. It has a tapioca-like starch[].
Flint corn, which shrinks on drying, can have white, yellow, purple, red or blue-black grains[]. It is not so sweet and also takes longer to mature so is a problematic crop in many temperate areas. There are many other uses for this plant as detailed below.
Dent corn has mostly white to yellow grains. This and Flint corn are widely grown for oils, cornflour, cereals and silage crops.
There are many named varieties[].

Edible Uses

Seed - raw or cooked. The immature seed can be eaten raw or cooked before it is fully ripe[, , , ] and there are varieties especially developed for this purpose (the sweet corns) that have very sweet seeds and a delicious flavour[, ]. The mature seed can be dried and used whole or ground into a flour. It has a very mild flavour and is used in a range of foods such as the Mexican tortillas and tacos, as a porridge, breakfast cereals, and as a thickening agent in foods such as custards[]. The starch is often extracted from the grain and used in making confectionery, noodles etc[].
The dried seed of certain varieties can be heated in an oven when they burst to make 'Popcorn'[]. The seed can also be sprouted and used in making uncooked breads and cereals[]. A nutritional analysis is available[].

Unripe cobs are consumed as a vegetable or green maize, boiled or roasted. Very young female inflorescences (‘baby cobs’) are a fancy vegetable in Western countries and in Asia[].
The fresh succulent 'silks' (the flowering parts of the cob) can also be eaten[, ]. Tender, delicious and highly nutritious[].

An edible oil is obtained from the seed, it is an all-purpose culinary oil that is frequently used as a food in salads and for cooking purposes[, , , ].

The pollen is used as an ingredient of soups[]. Rich in protein, it is harvested by tapping the flowering heads over a flat surface such as a bowl. Harvesting the pollen will actually help to improve fertilisation of the seeds[].
The roasted seed is a coffee substitute[].

The pith of the stem is chewed like sugar cane and is sometimes made into a syrup[].

Young developing leaves are tender and delicious[]. They can be eaten raw or cooked[]. Harvesting the leaves usually destroys the growing tip of the plant[].

The ash of the burnt stem is sometimes asubstitute for salt[].

Medicinal

The corn silks are cholagogue, demulcent, diuretic, lithontripic, mildly stimulant and vasodilator[, , , , ]. They are used primarily as a diuretic in the treaanent of conditions such as heart disease, hypertension, cystitis, urethritis, hepatitis, gonorrhoea, gout and rheumatism. Because they also act to reduce blood sugar levels, they are used in the treatment of diabetes mellitus[, , , ].
The silks are harvested before pollination occurs and are best used when fresh because they tend to lose their diuretic effect when stored and also become purgative[].

A decoction of the leaves and roots is used in the treatment of strangury, dysuria and gravel[].

A decoction of the cob is used in the treatment of nose bleeds and menorrhagia[].

The seed is diuretic and a mild stimulant[]. It is a good emollient poultice for ulcers, swellings and rheumatic pains[], and is widely used in the treatment of cancer, tumours and warts[]. It contains the cell-proliferant and wound-healing substance allantoin, which is widely used in herbal medicine (especially from the herb comfrey, Symphytum officinale) to speed the healing process[].

The plant is said to have anticancer properties and is experimentally hypoglycaemic and hypotensive[].

Agroforestry Uses:

Maize may be grown as a sole crop or in intercropping with other food crops such as common bean, cowpea, pigeon pea, groundnut, yam, cassava, sweet potato, pumpkin, melon or watermelon[].
Maize grows well with early potatoes, legumes, dill, cucurbits and sunflowers[, , ], it dislikes growing with tomatoes[].

Other Uses

A starch is obtained from the seed. It is used as a laundry starch and as a source material for many chemical products, including glues, cosmetics and the manufacture of glucose[, , ].

A semi-drying oil is obtained from the seed[]. It has many industrial uses, in the manufacture of linoleum, paints, varnishes, soaps etc[, , ].

The corn spathes are used in the production of paper, straw hats and small articles such as little baskets[, ]. They are often used to wrap foods, and may also be made into cloth or mats, and be used for mattress filling[].

A fibre obtained from the stems and seed husks is used for making paper[]. They are harvested in late summer after the seed has been harvested, they are cut into usable pieces and soaked in clear water for 24 hours. They are then cooked for 2 hours in soda ash and then beaten in a ball mill for 1½ hours in a ball mill. The fibres make a light greenish cream paper[]. Be careful not to overcook the fibre otherwise it will produce a sticky pulp that is very hard to form into paper[].

The dried cobs are used as a fuel and for thatching[, ].

The pith of the stems is used as a packing material[].

Propagation

Seed - sow mid spring in individual pots in a greenhouse. Grow on quickly and plant out after the last expected frosts. A direct outdoor sowing, especially of some of the less sweet varieties, can be tried in May.